glPushMatrix()和glPopMatrix()以及glLoadIdentity()的理解

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glLoadIdentity()重置当前矩阵，为什么要PushMatrix(),然后PopMatrix(),因为是由于是对矩阵进行变换，这样操作不至

于影响后面的矩阵操作。

Translate()每一次操作都把当前所在的位置作为原点。Rotate()每一次操作都是相对于当前原点的（而不是屏幕的中央）。

#include <windows.h>#include <GL/gl.h>#include <gl/glu.h>#include <gl/glut.h>void init(void){ glClearColor(0.0,0.0,0.0,0.0); glShadeModel(GL_SMOOTH); glClearDepth(1.0f);}void display(void){ glClear( GL_COLOR_BUFFER_BIT ); glShadeModel( GL_SMOOTH ); //现在原点绘制一个红色正方形 glColor3f( 1.0, 0.0, 0.0 ); glRectf( -0.05, -0.05, 0.05, 0.05 ); //glPushMatrix(); //变换--沿x轴移动 glTranslatef( 1.2, 0.0, 0.0 ); // glLoadIdentity(); // glPopMatrix();//再绘制一个正方形glColor3f( 0.0, 1.0, 0.0 );//glRectf( -0.05, -0.05, 0.05, 0.05 );//这时，当我们还想在同样位置绘制时，却发现已经偏移glFlush(); glFlush();}void reshape(int w,int h){ glViewport(0,0,(GLsizei)w,(GLsizei)h); glMatrixMode(GL_PROJECTION); glLoadIdentity(); if(w<=h) glOrtho(-1.5,1.5,-1.5*(GLfloat)h/(GLfloat)w,1.5*(GLfloat)h/(GLfloat)w,-10.0,10.0); else glOrtho(-1.5*(GLfloat)w/(GLfloat)h,1.5*(GLfloat)w/(GLfloat)h,-1.5,1.5,-10.0,10.0); glMatrixMode(GL_MODELVIEW); glLoadIdentity();}void mouse(int button,int state,int x,int y)//鼠标函数{ switch(button) { case GLUT_LEFT_BUTTON: //按下左键 if(state==GLUT_DOWN) { } break; case GLUT_MIDDLE_BUTTON: //按下左键 if(state==GLUT_DOWN) { } break; case GLUT_RIGHT_BUTTON: //按下左键 if(state==GLUT_DOWN) { } break; default: break; }}void keyboard(unsigned char key,int x,int y){ switch(key) { case 27: exit(0); break; default: break; } glutPostRedisplay();}int main(int argc, char** argv){ glutInit(&argc,argv); glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB); glutInitWindowSize(500,500); glutInitWindowPosition(50,50); glutCreateWindow("测试"); init(); glutReshapeFunc(reshape); glutDisplayFunc(display); glutKeyboardFunc(keyboard); glutMainLoop(); return 0;}

参考文章：http://blog.sina.com.cn/s/blog_602c65870100e703.html